1. E Witten, Phys. Lett. B144, 351 (1984)
2. T Appelquist, A Chodos and P G O Freund, Modern Kaluza–Klein theories (Addison–Wesley, Reading, 1987)
3. A Chodos and S Detweiler, Phys. Rev. D21, 2167 (1980)
4. W J Marciano, Phys. Rev. Lett. 52, 498 (1984)
5. D Sahdev, Phys. Rev. D30, 2495 (1984)